Our laboratory is engaged in the elucidation of the metabolism and function of several low molecular weight proteins which are induced in eucaryotic systems after a challenge by the heavy metals zinc, copper, cadmium, mercury, silver, and gold. We have focused on the proteins induced in rat liver and in kidney; these are called matallothionein and chelatin. Zinc metallothionein and copper chelatin are rapidly turning over proteins in rat liver, whereas cadmium metallothionein remains at high levels for days. Induction of copper chelating by exogenous cooper also leads to the synthesis of zinc metallothionein, possibly due to a disturbance in endogenous zinc homeostasis. We have also obtained rabbit antibodies specific for each of the three rat liver proteins and are in the process of developing a radioimmunoassay for each of these proteins.